# Zooming in on fermions and quantum gravity

## TL;DR

This paper investigates the microscopic dynamics of fermions and quantum gravity within the asymptotic-safety framework, revealing a nonminimal coupling and analyzing its effects on the fixed point and matter interactions.

## Contribution

It demonstrates the unavoidable nonminimal derivative coupling in the UV and assesses its impact on the Reuter fixed point, supporting the asymptotic-safety scenario with fermionic matter.

## Key findings

- Presence of nonminimal derivative coupling between curvature and fermions in UV
- Backreaction on the Reuter fixed point is small for finite fermion numbers
- Higher-derivative couplings are subleading in the momentum-dependent vertex flow

## Abstract

We zoom in on the microscopic dynamics for fermions and quantum gravity within the asymptotic-safety paradigm. A key finding of our study is the unavoidable presence of a nonminimal derivative coupling between the curvature and fermion fields in the ultraviolet. Its backreaction on the properties of the Reuter fixed point remains small for finite fermion numbers within a bounded range. This constitutes a nontrivial test of the asymptotic-safety scenario for gravity and fermionic matter, additionally supplemented by our studies of the momentum-dependent vertex flow which indicate the subleading nature of higher-derivative couplings. Moreover our study provides further indications that the critical surface of the Reuter fixed point has a low dimensionality even in the presence of matter.